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| author | Artem Bityutskiy <artem.bityutskiy@linux.intel.com> | 2025-03-17 15:55:40 +0200 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2025-04-15 20:38:26 +0200 |
| commit | af3a1b6a18258168f09e4ebc014b368bb0e845b0 (patch) | |
| tree | 4fcfe2549eb4a7ea785f6bd00bb79a8484bf4fe5 | |
| parent | 6138f34515162340520b0415184367e12775f68a (diff) | |
Documentation: admin-guide: pm: Document intel_idle C1 demotion
Document the intel_idle driver sysfs file for enabling/disabling C1
demotion.
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Link: https://patch.msgid.link/20250317135541.1471754-3-dedekind1@gmail.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
| -rw-r--r-- | Documentation/admin-guide/pm/intel_idle.rst | 21 |
1 files changed, 21 insertions, 0 deletions
diff --git a/Documentation/admin-guide/pm/intel_idle.rst b/Documentation/admin-guide/pm/intel_idle.rst index 5940528146eb0..ed6f055d4b148 100644 --- a/Documentation/admin-guide/pm/intel_idle.rst +++ b/Documentation/admin-guide/pm/intel_idle.rst @@ -38,6 +38,27 @@ instruction at all. only way to pass early-configuration-time parameters to it is via the kernel command line. +Sysfs Interface +=============== + +The ``intel_idle`` driver exposes the following ``sysfs`` attributes in +``/sys/devices/system/cpu/cpuidle/``: + +``intel_c1_demotion`` + Enable or disable C1 demotion for all CPUs in the system. This file is + only exposed on platforms that support the C1 demotion feature and where + it was tested. Value 0 means that C1 demotion is disabled, value 1 means + that it is enabled. Write 0 or 1 to disable or enable C1 demotion for + all CPUs. + + The C1 demotion feature involves the platform firmware demoting deep + C-state requests from the OS (e.g., C6 requests) to C1. The idea is that + firmware monitors CPU wake-up rate, and if it is higher than a + platform-specific threshold, the firmware demotes deep C-state requests + to C1. For example, Linux requests C6, but firmware noticed too many + wake-ups per second, and it keeps the CPU in C1. When the CPU stays in + C1 long enough, the platform promotes it back to C6. This may improve + some workloads' performance, but it may also increase power consumption. .. _intel-idle-enumeration-of-states: |